ABSTRACT
In the presence of a Pd(0) precatalyst, Pd2(bq)2(nbe)2 or Pd2(dba)3, 1,6-enyne esters were heated in refluxing benzene to give cyclodimers as single regioisomers. On the other hand, the combination of the Pd(0) precatalyst and triphenyl phosphite gave rise to various cycloisomerization products depending on the substitution pattern of the enyne esters. Six-membered ring cycloisomerization products were predominantly obtained from enyne esters bearing methallyl or 2-phenyl-2-propenyl moieties, while other enyne esters afforded normal five-membered ring cycloisomerization products. Intramolecular [2 + 2 + 2] cyclocotrimerization of enediyne esters also proceeded in the presence of the Pd(0) precatalyst and triphenylphosphine to give fused cyclohexadienes.
ABSTRACT
In the presence of 2.5 mol % of [Pd(2)(dba)(3)] (dba=dibenzylideneacetone) and 5 mol % of PPh(3), nearly equimolar amounts of dimethyl nona-2,7-diyne-1,9-dioate derivatives (diyne diesters) and dialkyl acetylenedicarboxylates were allowed to react in toluene at 110 degrees C to afford [2+2+2] cycloadducts in moderate-to-good yields. Similarly, dimethyl trideca-2,7,12-triyne-1,13-dioate derivatives (triyne diesters) were catalytically transformed into phthalic acid ester analogues in excellent yields. To gain insight into the mechanism of these intramolecular alkyne cyclotrimerizations, stoichiometric reactions of [Pd(2)(dba)(3)] with a diyne diester and a triyne diester bearing ether tethers were conducted in acetone at room temperature to furnish an oligomeric bicyclopalladacyclopentadiene and a Pd(0) triyne complex, respectively. The structures of these novel complexes were unequivocally determined by Xray structure analysis. The isolated triyne complex was heated at 50 degrees C or treated with PPh(3) in acetone at room temperature to afford the arene product. Furthermore, the same complex catalyzed the triyne cyclization with or without PPh(3).
ABSTRACT
The speciation of diverse elements in salmon egg cell cytoplasm was performed by a surfactant-mediated HPLC/ICP-MS hyphenated system. In the present experiment, an ODS column coated with CHAPS (3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate), which is a zwitterionic bile acid derivative, was employed as a surfactant-mediated separation column, and ICP-MS was used as an element-selective detector. The present surfactant-mediated HPLC allowed us to separate large and small molecules within 10 min; large molecules, such as proteins, were eluted within 2.5 min, while small molecules were eluted after 2.5 min, but within 10 min. In the present experiment, Fe, Cu, and Zn in egg cell cytoplasm were observed mostly in species with large molecular weights, indicating that these elements are contained as metalloproteins or metalloenzymes in egg cell cytoplasm. On the contrary, it was found that P, S, Mo, and halogens in egg cell cytoplasm were contained as small molecules or inorganic ions. The major species of P in egg cell cytoplasm was identified as the phosphate ion (PO4(3-)). Molybdenum, Cl, and Br in egg cell cytoplasm were molybdate (MoO4(2-), chloride (Cl-), and bromide (Br-) ions, respectively.
